1. Field of the Invention
The present invention relates to a catalyst system for plastics precursors which may be hardened using oxygen and contain organically bound mercapto groups.
2. Description of the Prior Art
Oligomers and polymers which contain at least two mercapto groups may be hardened, as is known, using oxidizing agents, such as MnO.sub.2, PbO.sub.2, chromates or organic peroxides, to form commercially valuable, rubber-like plastics materials (for example, German Offenlegungsschrift Nos. 2,739,117 and 2,557,088 or German Auslegeschrift No. 2,363,856). The hardening operation is generally carried out in two-component processes, in which the oxidizing agents are mixed with polymercaptans shortly before the processing step. The direct use of atmospheric oxygen as an oxidizing agent according to one-component processes is usually impossible since the reactivity is too low. For this reason, catalysts are becoming increasingly important for the accelerated oxidative hardening of oligomers containing mercapto groups. In this respect, combinations of thiuramdisulphides with iron or manganese complexes are suggested as catalysts, for example, in U.S. Pat. No. 3,991,039. Systems of dithiocarbamates with specific metallic carboxylic acid salts or complexes are recommended as catalysts in U.S. Pat. No. 4,224,200. However, the prior art catalyst systems which have been mentioned are still worth improving, in particular with respect to the through-hardening rate which may be achieved therewith.
According to the present invention, novel catalyst systems have been found for the area of use mentioned which are superior to the prior art catalyst systems with respect to their reaction-accelerating effect. A more rapid through-hardening of coating compositions containing plastics precursors with mercapto groups as the binder is obtained in particular by the use according to the present invention of novel catalyst systems described in more detail in the following.